In one form of liquid chromatography sample injection, the fluid path for handling the sample is pressurized. Such pressurization improves the sample movement speed by limiting the risk of vaporization of the sample. In order to control the degree of pressurization in such a system, a pressure gauge is typically installed in line with the pressure source. This pressure gauge is typically used in a feedback mode to control the generated pressure.
The increased pressure increases the likelihood of leakage at each of the multiple connection points that comprise the fluid path(s). Leaks may occur due to wear internal to a component, when a component is replaced due to faulty installation and also due to failures in joints at unexpected areas. For fluid movement systems that have small diameters, the volume of fluid leaking may be large enough to distort performance and yet small enough that it evaporates or is in some other way rendered invisible to inspection.
A system controller can use the output of the pressure gauge to tell that there is fluid leakage in the system when there is a greater than normal pressure drop in the system. However, this technique does not help to isolate the source of the leak. Certain techniques may limit the search area for the leak rather than eliminate leak target areas.
Previous systems have been able to determine that there is a leak in the system, but have not been able to identify the location of the leak nor identify points without leaks. Therefore, repair operations have typically involved disconnecting all connections, replacing many active components and essentially rebuilding the fluid movement system when a leak became too severe. Because of the extent of the repair activities, lesser leaks were allowed to remain until the system could be brought down for the major replacement operation.
Many pressurized injection systems require a cleaning cycle between successive usage cycles. In order to assure adequate cleaning, a set volume of cleaning fluid must pass through the system. In order to lessen the need for user interaction, the systems are set up for the extremes of operation. Since viscous liquids will take longer to flow through the system in a cleaning cycle, sufficient time is allocated for the most viscous fluid anticipated to execute the cleaning cycle. For all other fluids, some part of this time is wasted. If the viscosity of the fluid were known, the operation of the cleaning cycle could be tailored to optimize the fluid path cleaning cycle.
Diagnostics for fluid systems would allow inefficient and/or failing components to be identified. One set of information available is the expected pressure and pressure decay within a fluid system. If the actual pressures experienced by the system can be measured, comparisons can be conducted against the expected values.
Repairing a leak involves first finding it. Identifying the leakage point is beneficial because the repair time is minimized. Another time when checking for leaks is important is when a component is replaced and reconnected with the fluid system.